Foamable polymeric styrene particles and the articles produced from such particles are well known in the art. Such articles include insulated building panels, decorative display objects, novelties, cushioning materials, floatation devices, hot or cold beverage containers, portable ice or cooling chests or boxes, etc. The principal utilitarian characteristics of such foamed articles are their light weight and good heat insulation qualities.
The foamable polymeric particles are generally prepared by impregnating the particles with from 1% to 20% by weight of a suitable expanding or blowing agent such as pentane. In producing the foamed articles, the impregnated particles, or beads, are first subjected to a pre-expansion step wherein the beads are heated with steam in an unconfined space to produce a prepuff having a relatively low density. The prepuffed beads are then placed into the desired confined mold and final expansion accomplished with the further introduction of steam, followed by cooling and removal of the molded article.
A prerequisite for the use of foamed articles in certain applications is that such foamed articles must exhibit reduced flammability. This would be particularly true of foamed articles or panels employed in building construction. While the prior art discloses a number of additives that can be employed to reduce the flammability characteristics of foamed articles, there remains much room for further improvement.